The purpose of this study was to examine the effects of yohimbine pretreatment on the self-administration of triazolam in subjects with histories of sedative abuse. Two issues of relevance to the behavioral pharmacology of drug abuse are being addressed: the first involved the development of procedures to measure sedative/anxiolytic drug self-administration; and, the second was to examine the effects of yohimbine pretreatment on triazolam self-administration. It is of basic theoretical, as well as clinical, interest to define methods to detect the effects of one drug on the self-administration of another drug. In addition, yohimbine has been shown to produce neuroendocrine changes and subjective mood states in humans which resemble anxiety. Thus, this study could provide important information related to hypotheses of drug abuse which ivolve psychiatric vulnerability factors.